Since you have visited another place and there is a guy saying that he figured it out on how to fix it, I suggest you to ask him and see whether you can get an advice or two from him. In fact, I personally think that you will have to try to explore the possibilities that you think of to look for a solution. Since it is asking for a domain name, a domain name has nothing to do with your computer. In fact, it is a website that you might be running, etc. just simply put something in the field and sees how it works.